As a reinforcement structure at a front side of a vehicle cabin which supports a steering wheel, an audio system, or the like in an automobile, an instrument panel reinforcement pipe (hereinafter also referred to as an “instrument panel R/F pipe”), a floor brace, and a cowl-to brace are used.
For example, as exemplified in FIG. 18, an instrument panel R/F pipe 100 is a circular tubular pipe member, extends in a width direction of a vehicle, and has respective ends fixed on front pillars (A pillars) (not shown). A steering column 106 is supported on the instrument panel R/F pipe 100 via a steering support 102 and a steering bracket 104.
A cowl-to brace 108 is placed in a front-and-rear direction of the vehicle, and supports the instrument panel R/F pipe 100 primarily in the front-and-rear direction of the vehicle. A front end of the cowl-to brace 108 is joined to a cowl panel 110 of the vehicle body. In addition, the cowl-to brace 108 is placed to incline toward a lower side of the vehicle, from the front end toward a rear end, and the rear end is joined to the instrument panel R/F pipe 100 via a bracket 112.
A floor brace 114 is placed in an up-and-down direction of the vehicle, and supports the instrument panel R/F pipe 100 primarily in the up-and-down direction of the vehicle. A knee air bag 118 is attached between an upper end and a lower end of the floor brace 114, for protecting knees of passengers (driver) in a vehicle collision.
The upper end of the floor brace 114 is joined to the instrument panel R/F pipe 100 via the bracket 112. The floor brace 114 is placed to incline toward a rear side of the vehicle, from the upper end toward the lower end. The lower end is joined to a side wall 116A of a floor tunnel 116.
Specifically, a bolt joint portion 121A to be bolt-joined to the side wall 116A of the floor tunnel 116 in the width direction of the vehicle is provided at the lower end of the floor braced 114. With the bolt joint in the width direction, it becomes possible to suppress an up-and-down movement of the floor brace 114 due to a sheering stress acting on a bolt shaft portion when a load in a longitudinal direction (the up-and-down direction) is applied to the floor brace 114.
The upper end of the floor brace 114 and the bracket 112 are similarly bolt-joined in the width direction of the vehicle. Specifically, bolt joint portions 121B and 121C to be bolt-joined in the width direction of the vehicle are provided in the floor brace 114. By employing a two-point support using the two bolt joint portions 121B and 121C, it becomes possible to restrict a rotation of the floor brace 114.
That is, when the cowl-to brace 108 relatively moves in the front-and-rear direction of the vehicle with respect to the floor tunnel 116, a rotational load having a pivot on the bolt joint portion 121A is applied to the floor brace 114. If the floor brace 114 rotates with the bolt joint portion 121A as a pivot, a placement angle (relative angle) between the floor brace 114 and the bracket 112 would change. However, because the floor brace 114 and the bracket 112 are joined by the two bolt joint portions 121B and 121C, such a rotation is restricted.
Here, for example, in JP 2007-331614 A, there is employed a configuration, for the bolt joint as described above, in which a U-shaped hole with a partial cutout is employed for the bolt hole through which a stud bolt is inserted when skeleton members are joined with each other using the stud bolt and the bolt hole.
In the structure of the related art, during collision from the front side of the vehicle (hereinafter also referred to as a “front collision”), there remains room for improvement of the support of the floor brace. As exemplified in FIG. 19, at the time of front collision, an engine unit 120 is moved backward toward the rear side of the vehicle by an obstructing object (a barrier). With this process, the devices, panels, or the like behind the engine unit 120 are also moved backward. Specifically, an exhaust pipe 122 provided behind the engine unit 120 is moved backward while being deformed. Further, a dash panel 124 behind the exhaust pipe 122 is pushed by the exhaust pipe 122 and is moved backward. With this process, the cowl panel 110 joined to the upper end of the dash panel 124 and the cowl-to brace 108 joined to the cowl panel 110 are also moved backward. With the backward movement of the cowl-to brace 108, the upper end of the floor brace 114 joined to the rear end of the cowl-to brace 108 is also moved backward.
With the deformation and backward movement of the exhaust pipe 122, the floor tunnel 116 storing the exhaust pipe 122 is also deformed from the front side. Because the floor brace 114 having the lower end joined to the floor tunnel 116 has a structure in which the floor brace 114 extends in a manner to incline toward the rear side of the vehicle, from the upper end toward the lower end, the lower end of the floor brace 114 is placed slightly behind the front end of the floor tunnel. Therefore, at the time of the front collision, a certain time is required until the deformation reaches the bolt joint portion 121A at the lower end of the floor brace 114, and a backward-moving load may be applied to the upper end of the floor brace 114 before such deformation takes place. In this case, a rotational load F1 which is clockwise in a side view is applied to the floor brace 114, with the bolt joint portion 121A at the lower end as the pivot and the upper end as a point of application of the force.
When the bolt holes of the bolt joint portions 121B and 121C of the floor brace 114 have the U-shape, as in JP 2007-331614 A, there is a possibility that the floor brace 114 moves out of the bracket 112 by the rotational load F1, and it becomes unable to support the upper end of the floor brace 114.
On the other hand, when a closed circular shape is employed for the bolt holes of the bolt joint portions 121B and 121C of the floor brace 114, the rotation of the floor brace 114 is restricted by the two-point support as described above, and the floor brace 114 is deflected as exemplified in FIG. 19. With the deflection, a sheering force is applied to the bolt shaft portions of the bolt joint portions 121B and 121C. When the shock of the front collision is large, and an amount of deflection of the floor brace 114 is large, the sheering force applied to the bolt shaft portion may become excessive, rupturing or detachment of the bolt may occur, and it may become unable to support the upper end of the floor brace 114.
In either of the above-described cases, with the support of the upper end of the floor brace 114 being terminated, the support of the knee air bag 118 attached to the floor brace 114 also becomes unstable. In this manner, in the structure of the related art, there remains room for improvement from the viewpoint of the support of the floor brace 114, and, consequently, the support of the knee air bag 118 fixed on the floor brace 114.
An advantage of the present disclosure lies in the provision of a reinforcement structure at the front side of the vehicle cabin, which can sustain the support of the upper end of the floor brace 114 at the time of the front collision.